Radio access networks (RANs) provide for radio communication links to be arranged within the network between a plurality of user terminals. Such user terminals may be mobile and may be known as ‘mobile stations’ or ‘subscriber devices.’ At least one other terminal, e.g. used in conjunction with subscriber devices, may be a fixed terminal, e.g. a control terminal, base station, eNodeB, repeater, and/or access point. Such a RAN typically includes a system infrastructure which generally includes a network of various fixed terminals, which are in direct radio communication with the subscriber devices. Each of the fixed terminals operating in the RAN may have one or more transceivers which may, for example, serve subscriber devices in a given region or area, known as a ‘cell’ or ‘site’, by radio frequency (RF) communication. The subscriber devices that are in direct communication with a particular fixed terminal are said to be served by the fixed terminal. In one example, all radio communications to and from each subscriber device within the RAN are made via respective serving fixed terminals. Sites of neighboring fixed terminals may be offset from one another or may be non-overlapping or partially or fully overlapping.
RANs may operate according to an industry standard protocol such as, for example, an open media alliance (OMA) push to talk (PTT) over cellular (OMA-PoC) standard, a voice over IP (VoIP) standard, or a PTT over IP (PoIP) standard. Typically, protocols such as PoC, VoIP, and PoIP are implemented over broadband RANs including third generation and fourth generation networks such as third generation partnership project (3GPP) Long Term Evolution (LTE) networks. Communications in accordance with any one or more of these standards, or other standards, may take place over physical channels in accordance with one or more of a TDMA (time division multiple access), FDMA (frequency divisional multiple access), OFDMA (orthogonal frequency division multiplexing access), or CDMA (code division multiple access) protocols. Subscriber devices in RANs such as those set forth above send user communicated speech and data, herein referred to collectively as ‘traffic information’, in accordance with the designated protocol.
Many public safety narrowband RANs provide for group-based radio communications amongst a plurality of subscriber devices such that one member of a designated group can transmit once and have that transmission received by all other members of the group substantially simultaneously. Groups are conventionally assigned based on function. For example, all members of a particular local police force may be assigned to a same group so that all members of the particular local police force can stay in contact with one another, while avoiding the random transmissions of radio users outside of the local police force.
Either randomly or in response to an incident or event, such as a fire or accident, a number of subscriber device group members may congregate to within a single RF site. Due to the nature of the broadband connection, each group member subscriber device is conventionally provided with a separate unicast downlink over the broadband RAN. Accordingly, for example, if ten (10) subscriber devices in a group have roamed into a single RF site of a conventional broadband RAN, a corresponding fixed node serving that site receives group call data during an active group call from an infrastructure device via ten separate unicast transmissions over a backhaul downlink to the fixed node, and provides the group call data to each of the ten subscriber devices over ten separate unicast air interface downlinks (e.g., channels). Accordingly, if too many group subscriber devices roam into the single RF site, or the call data being communicated consumes substantial bandwidth (e.g., video, audio/video, etc.) there arises a risk that the backhaul downlink capacity, fixed node processing capability, or available air interface downlink capacity may become overloaded, perhaps resulting in reduced call data quality, dropping of connections to some or all group member subscriber devices, or other types of service interruptions or delays.
For example, when the event or incident occurs, numerous different groups may respond to the incident, including for example, first responders such as police, fire, and medical groups and supporting responders such as utility, traffic control, crowd control groups, among others. Each of these groups may attempt to, and may actually secure, resources on one or more of the broadband RANs available at the incident location. Given the limited availability of broadband RF resources on any one RAN available at or near the incident location, however, subscriber devices that are members of the first responders groups and/or supporting responders groups may be unable to secure broadband RF resources at the incident scene, resulting in an inability of some or all members of each group to communicate with other members of the group
For example, as shown in FIG. 1, an example broadband RAN 100 may include a first fixed node 102 serving RF sites 104 and 105, and a second fixed node 108 serving RF sites 104, 110, and 111. Fixed node 102 may be coupled to fixed node 108 and to a call controller 114 via a network 112 and a backhaul including downlink 116 and uplink 117. Fixed node 108 may similarly be coupled to fixed node 102 and to the call controller 114 via the network 112 and a backhaul including downlink 118 and uplink 119. Although not illustrated here, network 112 may include any number of additional infrastructure equipment to support group calls, including but not limited to switches, routers, gateways, authentication systems, subscriber device registration and location systems, system management, and other devices providing other operational functions.
In one example, broadband RAN 100 may be an LTE network and fixed nodes 102 and 108 eNodeBs. Network 112 may include an LTE evolved packet core, and subscriber devices being served by eNodeBs 102 and 108 may include compatible LTE transceivers. Communications sent over the LTE eNodeBs may be one of a varied number of communications types, including the above-mentioned data, voice (including OMA-PoC, VoIP, or PoIP), audio, video, audio/video, or some other type of media, perhaps transmitted using one or more other voice or data protocols such as real-time transport protocol (RTP) or session initiation protocol (SIP). Group call distribution may be handled at the call controller and evolved packet core via repeated IP unicast transmissions to each subscriber device in the group.
The LTE evolved packet core may contain known sub-systems required for operation of the LTE RAN. Such sub-systems may include, for example, sub-systems providing authentication, routing, subscriber device registration and location, system management and other operational functions within the LTE RAN. For example, the LTE evolved packet core may include one or more devices including, for example, a serving gateway (S-GW), a mobile management entity (MME), a home subscriber server (HSS), a Policy and Charging Rules Function (PCRF), and a packet data network (PDN) gateway (P-GW). The S-GW may function to route and forward data packets, while also acting as a mobility anchor for the user data plane during inter-eNodeB handovers and as the anchor for mobility between LTE and other 3GPP technologies, among other possibilities. The MME may function to track and page idle subscriber devices, authenticate subscriber devices (via interactions with the HSS), enforce subscriber device roaming restrictions, and handle security, key management, among other possibilities. The HSS may provide a central database that contains user-related and subscription-related information and may aid in subscriber device system roaming, call and session establishment support, and user authentication and access authorization. The PCRF may function to provide charging and credit control for user data flows, and may provide for QoS assignments to user data flows. The P-GW may function to provide connectivity from the served subscriber devices to external packet data networks (such as IP network or a POTS network) by being the point of exit and entry of traffic for the subscriber devices. The P-GW may also be involved in performing policy enforcement, packet filtering, and charging support. Fewer or more, and other types of, infrastructure devices may also be present and/or incorporated into the evolved packet core. The broadband RAN 100 in FIG. 1 may be an LTE RAN.
As illustrated in FIG. 1, three subscriber devices 120a, 120b, and 120c belonging to a first subscriber group have registered with the broadband RAN at fixed node 102 and have established separate unicast downlinks (three over backhaul downlink 116 and air interface downlinks 152-156). Similarly, three subscriber devices 130a, 130b, and 130c also belonging to the first subscriber group have registered with the broadband RAN at fixed node 108, and have established separate unicast downlinks (three over backhaul downlink 118 and air interface downlinks 157-160). Finally, three subscriber devices 140a, 140b, and 140c also belonging to the first subscriber group are outside of the range of the broadband RAN 100 or turned off, and have thus not established any connections with the broadband RAN 100. All subscriber devices in FIG. 1, with the exception of subscriber device 130c, are illustrated as mobile radios. Subscriber device 130c is illustrated as a vehicular subscriber device having a larger battery source and larger transmit power than the mobile radios. Of course, other types (including smart phones, cellular phones, tablet computers, etc.), other mixtures of devices, and other numbers of subscriber devices could be used in different scenarios and in other embodiments.
In the state illustrated in FIG. 1, and assuming a user at subscriber device 130a desires to transmit a call to the first subscriber group, a new group call request is transmitted to call controller 114 over air interface uplink 150, corresponding backhaul uplink 119, and network 112. Call controller 114 receives the new group call request, identifies the target group (the first subscriber group) indicated in the new group call request (e.g., associated with the group identified in the new group call request), and identifies the active target subscriber devices subscribed to the first subscriber group, including subscriber devices 120a, 120b, 120c, 130b, and 130c. The call controller 114 than acknowledges the new group call request to the source subscriber device 130a, and routes subsequently received call data from the source subscriber device 130a to the active target subscriber devices 120a, 120b, 120c, 130b, and 130c in the first subscriber group via separate unicast transmissions over backhaul downlinks 118, 116 and over separate air interface downlinks 152-156, 158, and 160. In other words, call controller 114 duplicates call data packets received from source radio 130a for each target subscriber device and sends the duplicated data via separate unicast downlinks to each target subscriber device subscribed to the group associated with the new group call request. Although not illustrated in FIG. 1, each target subscriber device 120a, 120b, 120c, 130b, and 130c also maintains separate unicast air interface uplinks for sending acknowledgments and/or control or status signaling to call controller 114 before, during, and/or after the group call. Due to the packet duplication and separate unicast downlinks used in conventional broadband RANs, this example group call initiated by source subscriber device 130a consumes five times (5×) the backhaul downlink 116, 118 bandwidth and air interface downlink 152-156, 158, 160 bandwidth as is used for a point to point (non-group) call. While group target subscriber devices are not too numerous, and/or are well distributed, conventional broadband RANs generally provide sufficient available bandwidth to meet the demands of such a group call.
However, and as illustrated in FIG. 2, as group target subscriber devices in broadband RAN 100 begin to congregate near one another, a demand on a limited available infrastructure may increase to a point that call quality is lowered or subscriber devices are unable to join or receive a group call. For example, in FIG. 2, subscriber device 120b has moved from RF site 104 to RF site 110 and is now receiving service from the broadband RAN 200 via fixed node 108. Subscriber devices 140a-c have powered on and/or moved into RF site 110 as well. Accordingly, for a same group call sourced from subscriber device 130a, call controller 114 must duplicate the call data eight times (8×), six of which traverse backhaul downlink 119 and separate unicast air interface downlinks 158-168. In some instances, this level of call data transmission load may be reaching, or already reached, a maximum load capacity at the fixed node 108, perhaps due to limited infrastructure backhaul downlink capacity, limited processing capacity at the fixed node 108, or air interface capacity at the fixed node 108, among other possibilities. As a result, existing calls, including the first group call described above, may exhibit decreased quality, and additional subscriber devices may be denied or unable to continue receiving existing calls or create or join new calls. For example, in one scenario, subsequently arriving fire incident responders may be unable to register with the broadband RAN 100 via fixed node 108, or may be denied the transmission of a new call to other fire incident responders or dropped from an existing call, due to a lack of sufficient resources in the broadband RAN 100.
Accordingly, there is a need for an improved solution that would allow an infrastructure device, such as call controller 114, to improve efficiency of group calls over broadband RANs by selectively consolidating unicast downlinks in the broadband RAN for a requested new group call, and to manage the consolidation during the group call.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present disclosure.